Drill bit design has a long history and several improvements and new concepts have been developed to improve the performance of drill bits used down-hole in wells, such as oil wells or gas wells, and to adapt different drill bit characteristics to different drilling environments and to different drilling requirements while down-hole in a well.
One of the issues with existing design of drill bits is the need to trip the whole drill string or drilling apparatus out of the hole in order to change the bit when drilling environments or the drilling requirements change during drilling. This is an expensive exercise as drilling activities have to be stopped for a period of time while this is being done. The need to trip the whole drill string or drilling apparatus also exists when the cutting elements on the bit are damaged or lost in use and they need to be replaced for efficient drilling to continue.
Despite significant development over the years, drill bit designs have remained concentrated on the solid architecture of the drill bit. There were various reasons for this, such as; previously drill bits used in wells were designed to be used connected with tubes to the surface, with poor control of drilling conditions. Also when drilling with tubes connected to surface, it was difficult to control the force applied to the drill bit and the design of the drill bit always then included a large safety coefficient to provide resistance to the very high loads that were possible. In addition, when drilling with tubes connected to the surface of a well, it was not practical to implement control of actuators mounted on the drill bit. Further, when drilling with tubes connected to surface, it was not possible to rotate the drill bit in both directions for drilling. This was due to the tube being made with a thread in one direction that could take a torque load in that one direction but could not take a torque load in the other direction without a risk of the thread breaking.
A steerable drilling system is described in GB 2428713 A as having a drill bit which includes one or more moveable components. The movable component is shown as being mounted on a blade of the drill bit, and on which is provided a plurality of cutting elements. The advantages which the current invention has over the drilling system and drill bit as disclosed in that document, is that the rotary drill bit of the present invention may be used in the changing drilling environments and drilling requirements where conventional drilling with pipes are used. The current invention provides for improved steering, vibrations to ease cuttings, milling, and adaption to change in rocks, et cetera, in environments where the stresses on the drill bit are very high and where access to control over the drill bit are limited. Further, the current invention is operable in at least two different drilling orientations and the drilling surface is rotatable in one of two opposing directions, allowing for efficient adaption to any changes in the drilling environment.
One of the advantages of the current invention is that the drill bit characteristics may be adapted to changes in the drilling environment in a well or to changes in the drilling requirements in a well, without having to pull the drilling equipment out of the well. The adaptations made to the characteristics of the drill bit may also have the advantage that they improve the performance of the drill bit in a changing drilling environment or under changing drilling requirements. The drill bit may be used in more than one rotary direction and orientation of the cutting elements and the cutting surfaces on the cutting elements may all be adjusted according to what is required in the particular circumstances without having to remove the drilling equipment from the drilling area. Further, the drill bit may be adapted remotely.
Another advantage of the current invention is that when used in open mining the drill bit characteristics may be remotely adapted to changes in the drilling environments and changing drilling requirements.